Artificial dentures



Feb. 28, 1967 A. GERBER 3,305,926

ARTIFIC IAL DENTURES Filed Nov. 4, 1963 2 Sheets-Sheet 2 INVENTOR ALBERTGERBER W Q M A'ITORNEYS United States Patent Ofiice 3,305,9Z6 PatentedFeb. 28, 1967 3,305,926 ARTIFICIAL DENTURES Albert Gerber, 11Plattenstrasse, Zurich, Switzerland Filed Nov. 4, 1963, Ser. NO. 321,118Claims riority, application Switzerland, Nov. 9, 1962, 13,155/ 62 2Claims. (Cl. 32-2) The present invention broadly has reference toimprovements in artificial posterior teeth for dentures.

A large number of forms have been developed for the manufacture ofartificial posterior teeth for dentures which partially deviate only toa small extent and partially deviate to a 'large extent from the form orshape of natural posterior teeth (premolars and molars). Such deviationshave 'been undertaken in order to accommodate the particular static andmechanical laws to which all full dentures are subjected. Furthermore,these deviations 'from the natural shape are undertaken in order toreduce the contact surfaces of the artificial posteriors in all gliding-movements of the lower jaw. From the entire number of possible patternsand paths of movement of the lower jaw only those are .of interest whichresult in an antagonistic friction of the artificial posteriors.

Since there are still considerable diiferences between the varioustheories on the geometry of these movements of the lower jaw, theartificial teeth also differ appreciably in regard of the relevantmovement Characteristics of the -mastcation surfaces of the artificialteeth, according as the teeth are based upon this or that theory. Sincethe manufacturing laboratories or plants which produce artificial teethare, as a rule, generally advised by persons specialised in the theoriesof -occlusion and articulation movements, the different artificial teethcan generally be easily distinguished from one another by the skilledperson in view of the characteristic features, and insofar as suchmanufactures do not merely copy the purely anatomical shape of naturalteeth. Generally it can be considered that in the formation ofartificial chewing and gliding surfaces of posterior teeth threeform-influencing factors are placed in the foreground by Specialists inprosthetic dentistry.

(1) The intention to accommodate the artificial teeth shapes and chewingsurface shapes to the particular static and dynamic laws to which allfull dentures are subjected requires deviations from the anatomicalshape of natural teeth.

(2) The intention to accommodate the artificial teeth shapes and chewingsurface shapes to the theories advanced respectng the geometry of themovement of the lower jaw likewise requires appropriate devi-ations fromthe anatomical shape of newly erupted natural teeth.

(3) The intention to provide the chewing surfaces of the lower and upperarches of teeth with effective elements for mechanical chewing, such asedges, ridges and so forth, likewise oftentimes requires deviations fromthe anatomical shape -of natural premolars and molars. Such deviationsare also undertaken to protect the living tissues, such as 'bone andmucous membrane supporting the dentures. For the protection of theliving tissues there is required, in accordance with generally acceptedprinciples, high chewing efliciency even with small muscle forces, aswell as antagonistic gliding movements free of cusp-interference toprotect the denture supporting tissue from excessive thrust and shearcomponents.

The combination of the intentions enumerated in items l to 3, has inactual practice very often led to artificial premolar and molar teethwhich in minor and major points deviated from the shape of natural teethchewing surfaces and the shapes of which were based upon purelytechnical considerations.

It has *been suggested to Combine factors 1 to 3 above 'with thefollowing factor:

(4) The intention to preserve as nearly as possible the anatomicalappearance and shape of natural teeth without neglecting thebiomechanical particularities of full dentures.

Not infrequently with the construction of arches of artificial teeth itis also necessary to provide a very considerable deviation -from thewidth of natural premolars and molars. Practical experience has namelyshown that not infrequently, in the construction of artificial teeth forthe lower jaw, there must be taken into Consideration that the tonguemay have increased in size as a result of partially edentulous ridges.If such is the case, when the lower denture is fitted there is onlyavailable a very narrow space between tongue and Cheek. In order tocover such not too seldom occurring requirement with particularlyspacesaving posterior teeth, there are available on the market, inaddition to standard shapes, also special sets of teeth with narrowpremolars and molars.

In order to also accommodate -for such a situation without broadeningthe fabricated assortment of teeth shapes or forms the inventioncontemplates the following:

(5) New shapes of artificial posterior teeth are developed for the upperjaw as well as the lower jaw which correspond to the features mentionedunder items l to 4 and, at the same time, are constructed in proportionsand chewing surface forms in such a manner that the usual assembly ofeight teeth for the lower denture can be composed for special cases fromonly eight premolars. Since premolars are much smaller than molars, rowsof Cheek teeth constructed -fr'om only such premolars can be insertedbetween tongue and Cheek for eifective function even with a shortage ofspace.

This aim can then be considered as accomplished when in a dentallaboratory a set of eight lower premolars can be put into perfectantagonistic contact and occlusion with an upper normal set ofartificial posterior teeth, consisting of two premolars and two molarsfor each side.

While keeping the foregoing in mind, it Will be generally recognizedthat the present invention relates to an assembly of artificialposterior teeth characterized by the features that, for each pair ofsuperirnposed arranged teeth, one such tooth possesses a chewing groovewhich is concave in transverse or cross-section as well as also inlongitudinal section and the other tooth is provided with acorresponding cusp which cooperates with the chewing groove of the saidone tooth and which is conveX in transverse or cross-section as Well asalso in longitudinal section. Furthermore, the convex curvatures of theaforesaid protuberance have sharper curves than the concave curvaturesof the chewing groove cooperating with the protuberance. Moreover, thedeepest point of the chewing groove as viewed in transverse section isdisplaced towards the lingual side. Thus, the function-al area of the:chewing surface Can be more easily located on the inner '(lingual)field of the alveolar ridges.

The invention also takes into Consideration the fact that the closingmovement of the lower jaw is not always done with geometric precision.

Therefore, the o cclusion or intercuspidation of the artificial teethmust include a degree of tolerance.

In conjunction with the object of the invention there is provided arange of tolerance for slightly ditfering centric :positions of thelower jaw. Such tolerance is achieved in :that the radii of curvature ofthe surfaces which encounter one another are selected to be considerablysmaller for the convex surface than for the concave surface, to providef a mortar and pestle effect.

Further objects and advantages and the entire scope 'of applicability ofthe present invention will become apparent from the detailed descriptiongiven hereinafter; it 'should be understood, however, that the detaileddescrip- ,tion -and specific examples, while indicating preferredembodiments of the invention, are given by way of illustra- :tion only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

In the drawings:

FIGURE 1 schematically illustrates a side view of the first upper andlower premolars designed according to the invention;

FIGURE 2 is a side view of the second upper and lower premolars;

FIGURE 3 is a side view of the first upper and lower molar;

FIGURE 4 illustrates a front view of an upper and lower row of teethconstructed in the manner of the teeth depicted in FIGURES 1-3;

FIGURES Sa to 5C are front views of a first upper molar and first andsecond lower molars designed according to the invention and theircooperative relation for different positions of the jaw in glidingmovements;

FIGURE 6 illustrates the right-side of a normal denture constructionwith two molars and two premolars arranged at the top and bottom; and

FIGURE 7 illustrates a view similar to FIGURE 6 but with a lower ro-w ofteeth incorporating four premolars.

Describing now the drawings, in FIGURE 1 there are illustrated a sideview of the upper and lower first premolars. The lower tooth 11possesses a cutting edge-like cusp 12 which is in antagonism orcounteraction with a concave chewing surface Zone or groove 13 of theupper tooth 14 and possessing large radus. Reference numeral 15generally depicts the tongue, whereas numeral 16 represents a portion ofthe false teeth plate.

In FIGURE 2 there is illustrated a side view of the second premolars.The cusp 18 of the upper tooth 17 situated towards the tongue 15possesses a surface with a small radus of curvature and engages with acentral chewing groove or furrow 19 of the lower second premolar 20.Moreover, the central chewing groove 19 exhibits a considerably largerradus of curvature than the cusp 18. The protuberance 21 of the lowertooth possesses towards the side of the check a small flat or planesurface 22.

In FIGURE 3 there are illustrated the first upper and lower molars. Inthe same manner as in FIGURE 2 the upper tooth 23 in this case alsopossesses a cusp 24 which engages With a chewing groove or furrow 25 ofthe lower tooth 26, wherein the radus of curvature of the chewing groove25 is larger than that of the cusp 24. I-Iowever, the protuberance 24 ofthe upper tooth 23 in deviation from the natural model is here largerthan the buccal cusps 27, 28 arranged behind one another, of which onlythe cusp 27 is visible in this figure. At the lower tooth 26 the cusp 29towards the side of the check 30 in deviation from the anatomical shapeis constructed in reduced size and is provided with a pronouncedinclined plane surface 31 which dreps-off buccally. Analogous deviationsfrom natural models Or patterns are applied also to the chewing surfacesof the second premolars and the second molars in the interest ofimproving the static and dynamics of the denture constructions.

In FIGURE 4 there is illustrated a side View (next to the Cheek) of anupper and lower row of teeth provided with the teeth previouslydescribed in FIGURES 1-3. The construction is maintained in accordancewith a multiple mortar-pestle principle in that, in the lower row ofteeth the chewing groove 25 of a forward tooth continues to asubsequently arranged inclined surface 32 of a rearward tooth.

In FIGURES Sa to SC there is depicted the first upper molar an-d thefirst and second lower molars in side view for different positions of-the jaw. Thus, in FIGURE Sa the teeth -are located in the centralposition. The cusp 27 is disposed in the chewing groove 25 and the cusp2'8 upon the inclined surface 32 of the neighboring tooth. When thelower jaw slides back then the cusp 28 glides from the inclined surface32 of the rearward tooth into the chewing groove 25 of the forwardtooth, as best seen by referring to FnIGURE Sb. On the other hand, ifthe lower jaw is moved forwardly or projected then the positionindicated in FIGURE 5c is o-btained.

In FIGUR-E 6 there is illustrated in side view the right-sidedenticulation for -a nor-mal construction with two premolars 33, 34 andtwo molars 35 arranged at the top and bottom. In FIGURE 7 the sameright-side upper tooth row is illustrated in engagement with a lower rowof teeth incorporating four premolars. Thus, the first lower molar isreplaced by a second right-side premolar 34 and a second left-sidepremolar36. In this combination there is not inserted a lower secondmolar.

As illustrated in the figures, the portion of the cusp surfacescooperating with the chewing surface or groove is more sharply curvedthan the chewing surface or groove, producing a mortar and pestleeffect. In addition, the deepest part of the concave chewing surface orgroove is shifted towards the ling-ual side of the molar or premolar.Finally, a downwardly inclined planar surface 22 or 31 is locatedbuccally. The advanta-ge of the former is, as already remarked, that thefunctional area of -the chewing surface is more easily located on thelingual field of the alveolar ridges. The latter permits the food toslide down and off the surface and reduces the loading in the area ofthe ocelusion complex. The chewing grooves or surfaces are concave inboth longitudinal and transverse cross section.

While there is shown and described present preferred embodiments of theinvention it is to be distinctly understood that the invention -is notlimited thereto but may be otherwise variously embodied and practisedwithin the scope of the following clairns.

Having thus described the present invention, what is desired to besecured by United States Letters Patent, is:

1. A set of dentures, including: first upper and lower premolar teeth,said upper premolar tooth having .a chewing groove concave in transverseand longitudinal section, said lower premolar tooth having a cooperatingcusp convex in transverse and longitudinal section, said cusp bein-gmore sha-rply curved over its surface that cooperates with the groovethan said groove, and the deepest point of said groove in transversesection being displaced towards the lingual side of the tooth; secondupper and lower premolar teeth, said lower premolar tooth hav- 'ing achewing -groove concave in transverse and longitudinal section, saidupper premolar tooth having a cooperating cusp conveX in transverse andlongitudinal section, said cusp being more sharply curved over itssurface that cooperates with the groove than said groove, and thedeepest point of said groove in transverse section being displacedtowards the lingual side of the tooth; first and second upper and lowermolars, said upper molars each having at least two cusps, which cuspsare spaced transversely of the respective tooth and are convex intransverse and longi-tudinal section, said lower molars each 3,05,926 56 having a chewing groove cooperating with the said two wardly inclinedsubstantially planar surface located next cusps of the upper .toothwhich is concave in transverse to the check. and longitudinal section,said cusps being more sharply curved Over their surfaces that cooperatewith the respec- R f e Cit d by the Examiner tive grooves than the groove, and the deepest point of 5 said grooves in transverse sectionbeing displaced towards UNITED STATES PATENTS the lin-gual side of theteeth. 1 6/ 4 Luthy 2. The set of posterior teeth as defined in claim 1,including on said second lower premolar tooth and on ROB'ERT E. MORGAN,Acting Primary Exammer.

each of said first and second lower molar teeth a down- 10

1. A SET OF DENTURES, INCLUDING: FIRST UPPER AND LOWER PREMOLAR TEETH,SAID UPPER PREMOLAR TOOTH HAVING A CHEWING GROOVE CONCAVE IN TRANSVERSEAND LONGITUDINAL SECTION, SAID LOWER PREMOLAR TOOTH HAVING A COOPERATINGCUSP CONVEX IN TRANSVERSE AND LONGITUDINAL SECTION, SAID CUSP BEING MORESHARPLY CURVED OVER ITS SURFACE THAT COOPERATES WITH THE GROOVE THANSAID GROOVE, AND THE DEEPEST POINT OF SAID GROOVE IN TRANSVERSE SECTIONBEING DISPLACED TOWARDS THE LINGUAL SIDE OF THE TOOTH; SECOND UPPER ANDLOWER PREMOLAR TEETH, SAID LOWER PREMOLAR TOOTH HAVING A CHEWING GROOVECONCAVE IN TRANSVERSE AND LONGITUDINAL SECTION, SAID UPPER PREMOLARTOOTH HAVING A COOPERATING CUSP CONVEX IN TRANSVERSE AND LONGITUDINALSECTION, SAID CUSP BEING MORE SHARPLY CURVED OVER ITS SURFACE THATCOOPERATES WITH THE GROOVE THAN SAID GROOVE, AND THE DEEPEST POINT OFSAID GROOVE IN TRANSVERSE SECTION BEING DISPLACED TOWARDS THE LINGUALSIDE OF THE TOOTH; FIRST AND SECOND UPPER AND LOWER MOLARS, SAID UPPERMOLARS EACH HAVING AT LEAST TWO CUSPS, WHICH CUSPS ARE SPACEDTRANSVERSELY OF THE RESPECTIVE TOOTH AND ARE CONVEX IN TRANSVERSE ANDLONGITUDINAL SECTION, SAID LOWER MOLARS EACH HAVING A CHEWING GROOVECOOPERATING WITH THE SAID TWO CUSPS OF THE UPPER TOOTH WHICH IS CONCAVEIN TRANSVERSE AND LONGITUDINAL SECTION, SAID CUSPS BEING MORE SHARPLYCURVED OVER THEIR SURFACES THAT COOPERATE WITH THE RESPECTIVE GROOVESTHAN THE GROOVE, AND THE DEEPEST POINT OF SAID GROOVES IN TRANSVERSESECTION BEING DISPLACED TOWARDS THE LINGUAL SIDE OF THE TEETH.